package dao;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
public static void main(String [] args){
    String username= "use";
    Pattern compile = Pattern.compile("^[a-zA-Z0-9]{6,20}$");
    Matcher matcher = compile.matcher(username);
    boolean matches = matcher.matches();
    System.out.println(matches);
}


}

